• International Journal of Highway Engineering
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• v.17 no.1
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• pp.7-16
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• 2015

PURPOSES : This study was performed to determine a systematic approach for measuring the coefficient of thermal expansion (COTE) of concrete specimens. This approach includes the initial calibration of measurement equipment. Test variables include coarse aggregate types such as natural aggregate, job-site produced recycled concrete aggregate, and recycled aggregate processed from an intermediate waste treatment company. METHODS : First, two cylindrical SUS-304 specimens with a known COTE value of $17.3{\times}10^{-6}m/m/^{\circ}C$. were used as reference specimens for the calibration of each measurement system. The well-known AASHTO TP-60 COTE apparatus for concrete measurement was utilized in this study. Four different measurement apparatuses were used with each LVDT installed and a calibration value was determined using each measurement apparatus. RESULTS : In the initial experimental stage, calibration values for each measurement apparatus were assumed to be almost identical. However, using the SUS-304 samples as a reference, the calibration values for the four different measurement apparatuses were found to range from 3.49 to $8.86{\times}10^{-6}m/m/^{\circ}C$. Using different adjusted values for each measurement apparatuses, COTE values for the three different concrete specimens were obtained. The COTE value of concrete made with natural coarse aggregate was $9.91{\times}10^{-6}m/m/^{\circ}C$, that of job-site produced recycled coarse aggregate was $10.45{\times}10^{-6}m/m/^{\circ}C$, and that of recycled aggregate processed from the intermediate waste treatment company was $10.82{\times}10^{-6}m/m/^{\circ}C$. CONCLUSIONS : We observed that the COTE value of concrete made from recycled concrete aggregates (RCA) was higher than that of concrete made from natural coarse aggregate. This difference is due to the fact that the total volumetric mortar proportion in the RCA mix is higher than that in the concrete mix made with natural coarse aggregate.

• Journal of the Korean Society of Safety
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• v.32 no.5
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• pp.41-46
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• 2017

The coefficient of derailment and the rate of wheel load reduction were used as the index of train running safety that was directly affected the train derailment safety. In aspects of track, the train running safety depends on the complex interaction between wheel and rail, and the track-vehicle conditions (i.e., the curvature, cant, track system, vehicle speed and the operation conditions, etc). In this study, the relationship between the train running safety and the track curvature and vehicle speed for direct fixation concrete tracks currently employed in Korean light rapid transit was assessed by performing field tests using actual vehicles running along the service lines. The measured dynamic wheel load, lateral wheel load and lateral displacement of rail head were measured for same train running on four tested tracks under real conditions, which included curved and tangent tracks placed on the tunnel and bridge, thus increasing the train speed by approximately maximum design speed of each test site. Therefore, the measured dynamic track response was applied to the running safety analysis in order to evaluate the coefficient of derailment, the rate of wheel load reduction and the track gauge widening at each test site, and compare with the corresponding Korean train running safety standard. As the results, the lateral track response of direct fixation concrete track appeared to increase with the decreased track curvature; therefore, it was inferred that the track curvature directly affected the train running safety.

• Atmosphere
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• v.24 no.3
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• pp.317-329
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• 2014

Eddy covariance data have been analyzed to investigate the influence of surface heterogeneity on turbulent transfer over farmland and industrial sites near Nakdong river, Korea, where both large and small scale heterogeneities co-exist. For this purpose, basic turbulent statistics, quadrant analysis and multi-resolution decomposition have been analyzed during the daytime. Basic turbulent statistics were compared with typical turbulent statistics in the surface layer. Such comparisons were in close agreement for momentum and heat at both sites but not for water vapor at industrial site. The correlation coefficient between water vapor and vertical velocity ($r_{wq}$) is relatively low and skewness of water vapor ($sk_q$) is very low at industrial site, possibly due to limited water source. For heat at both sites and water vapor at farmland, the quadrant analysis show similar behavior to that over homogeneous site but for water vapor at industrial site, the presence of river and limited water source at industrial site seems to influence on water vapor transfer by coherent eddy motion by increasing sweep contribution and decreasing ejection contribution. Multi-resolution decomposition analysis shows that large scale heterogeneity leads to low $r_{Tq}$ at large averaging time regardless of season at both sites and there are seasonal changes of $r_{Tq}$ in mid-averaging times at industrial site, possibly due to seasonal change of trees and grasses near the site.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.3
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• pp.23-32
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• 2004

The local geologic and dynamic site characteristics, which include soil profiles, shear wave velocity profiles and depths to the bed rock were gathered from 148 sites all over the Korean peninsula and those values are compared to those in the western USA. Site response analyses were performed based on equivalent linear scheme using design rock-outcrop acceleration of 0.154g which corresponds to the collapse level of earthquake for seismic category I structure. The results show that the amplification factor based on Korean seismic design guideline underestimates the motion in short-period range and overestimates the motion in mid-period range. It is suggested that the existing Korean seismic guideline based on UBC is required to be modified considering dynamic site characteristics in Korea for the reliable estimation of site amplification.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.6
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• pp.875-885
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• 2019

This paper is aimed to suggest the coefficient of variation of the total load on the segment lining and the coefficient of variation of earth pressure in reliability based design of shield tunnel. For this purpose, the statistical characteristics of weathered soil and weathered rock were calculated by analyzing the site survey data of the domestic urban section. The coefficient of variation could be estimated by applying these values to Terzaghi's theory using MCS technique. As a result, the coefficient of variation of rock load for weathered soil and weathered rock was 0.08~0.14. The coefficient of variation for the total load acting on the tunnel was LC1 = 0.38, LC2 = 0.33, and LC3 = 0.37. The proposed coefficients of variation can be used in the reliability-based design of shield tunnel segments.

• Journal of the Korean Geotechnical Society
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• v.21 no.6
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• pp.101-115
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• 2005

For the site characterization at two inland areas, Gyeongju and Hongsung, which represent geomorphic and geologic characteristics of inland region in Korea, in-situ seismic tests containing borehole drilling investigations and resonant column tests were peformed and site-specific seismic response analyses were conducted using equivalent linear as well as nonlinear scheme. The soil deposits in Korea were shallower and stiffer than those in western US, from which the site coefficients and site classification system in Korea were derived. Most sites were categorized as site classes C and D based on the mean shear wave velocity $(V_s)$ of the upper 30 m $(V_s30)$, ranging between 250 and 650 m/s. According to the acceleration response spectra determined from the site response analyses, the site coefficients specified in the current Korean seismic design guide underestimate the ground motion in the short-period band and overestimate the ground motion in mid-period band. These differences can be explained by the differences in the bedrock depth and the soil stiffness profile between Korea and western US. The site coefficients, $F_a$ for short-period and $F_v$ for mid-period, were re-evaluated and the site classification system, in which sites C and D were subdivided according to $V_s20,\;V_s15,\;and\;V_s10$ together with the existing $V_s30$ was introduced accounting for the local geologic conditions at inland region of the Korean peninsula. The proposed site classification system in this paper is still rudimentary and requires modification.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.735-742
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• 2005

The purpose of this study was to evaluate the salt water resistance of concrete depending on various types of cement. In this regard, 5 types of concrete were selected and their strength, void ratio and chloride ion diffusion characteristics were tested, and mutual correlation were analyzed. From the test results, the compressive strength and void ratio of concrete which using Type V cement was as good as Type I cement at long-term ages but the chloride diffusion coefficient of Type V cement was larger than Type I cement. And the concrete replacing some portion of the Type I cement with fly ash was superior in the cases of compressive strength, void ratio and the resistance of chloride ion permeation compared to the Type I cement with the lapse of ages. On the other hand, the compressive strength, the void ratio and the chloride diffusion coefficient of the concrete all indicated high levels of the correlation coefficient and the coefficient of determination regardless of the type of cement.

• The Journal of Engineering Geology
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• v.25 no.2
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• pp.273-280
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• 2015

Delays in horizontal well drilling when encountering heterogeneous sediments can have negative effects on the construction process at a riverbank filtration site. Grain size analysis, including calculation of the coefficient of uniformity and the coefficient of curvature, was conducted on soil samples collected at each drilling depth during the process of drilling horizontal wells. These results were then used to develop a linear equation for estimating drilling velocity using the coefficient of uniformity and the coefficient of curvature as inputs. Testing of the linear equation in other horizontal wells indicates that the equation is most appropriate for coarse-sand-sized and well-sorted sediment. Because this study was conducted in a region with small- to medium-sized streams, more data are needed from larger rivers to modify the general equation. Our results will provide better estimates of drilling velocity, in turn enabling more detailed design and more effective construction management at riverbank filtration sites.

• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.151-159
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• 2004

This paper describes a systematic way of identifying the horizontal coefficient of consolidation of clayey soil by applying an optimization technique to the early part of dissipation data measured from the self-boring pressuremeter strain holding test. An analytical solution developed by Randolph ＆ Wroth (1979) was implemented in normalized form to express the build-up of excess pore pressures as a function of the rigidity index and subsequent dissipation of excess pore pressures around a pressuremeter Horizontal coefficient of consolidation was determined by minimizing the differences between theoretical and measured excess pore pressure curves over 50% degree of dissipation range using optimization technique. The effectiveness of the proposed back-analysis method was examined against the real fled performances obtained from pressuremeter strain holding tests at Gimje and Yangsan site. It is shown that the proposed back-analysis method can evaluates the rational horizontal coefficient of consolidation, which is similar to those obtained from the piezocone dissipation test. Furthermore, proposed method can evaluate appropriate coefficient of consolidation for soil under partially drained condition.

• Land and Housing Review
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• v.5 no.2
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• pp.115-120
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• 2014

Site coefficient and amplification factor of current domestic Seismic Design Code (KBC-2009) have no consideration for the domestic ground condition in which the base rock is normally placed within 30m form the surface. Accordingly, in this study dynamic centrifugal test and analysis for pile foundation into clay were achieved. and the response spectrums of free surface and basement were compared with each other. Within the period 1sec., the measured spectral acceleration of free surface and basement was bigger than the design spectral acceleration of SC and SD site. However the measured spectral acceleration of free surface and basement for the period over 1.5sec. was smaller than the design spectral acceleration of SC site. There was no severe difference of spectral acceleration according to the upper structure, embedded depth of foundation and free surface conditions. Consequently, normal domestic apartment housing for the period range over 1.5sec. could be design more economically applying these test result.